Focus ring and substrate processing apparatus having same

ABSTRACT

There is provided a focus ring that is capable of preventing deposits from adhering to a member having a lower temperature in a gap between two members having different temperatures. A focus ring  25  is disposed to surround a peripheral portion of a wafer W in a chamber  11  of a substrate processing apparatus  10.  The focus ring  25  includes an inner focus ring  25   a  and an outer focus ring  25   b.  Here, the inner focus ring  25   a  is placed adjacent to the wafer W and configured to be cooled; and the outer focus ring  25   b  is placed so as to surround the inner focus ring  25   a  and configured not to be cooled. Further, a block member  25   c  is provided in a gap between the inner focus ring  25   a  and the outer focus ring  25   b.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2011-002250 filed on Jan. 7, 2011, and U.S. Provisional Application Ser.No. 61/435,086 filed on Jan. 21, 2011, the entire disclosures of whichare incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a focus ring and a substrateprocessing apparatus having the focus ring.

BACKGROUND OF THE INVENTION

Recently, as a semiconductor wafer (hereinafter, simply referred to as a“wafer”), on which semiconductor devices is to be formed, is scaled up,it has been required to manufacture semiconductor devices even on aperipheral region of the wafer W, e.g., on a range within about 10 mmfrom an edge of the wafer toward a center thereof. Usually, atemperature distribution of the wafer affects a distribution of radicalsin plasma by which a plasma process is performed on the wafer. Thus, inorder to perform a uniform plasma process on the entire region of thewafer, the temperature of the peripheral region of the wafer needs to becontrolled to be substantially the same as the temperature of the otherregion of the wafer. For the purpose, conventionally, there has beendeveloped a technique for controlling the temperature of the focus ringto cool the focus ring in order to reduce radiant heat from the focusring.

However, if the entire wafer temperature becomes lower as the focus ringis cooled, a resist film coated on the wafer as a pattern mask is easilyetched by the plasma. Thus, in order to prevent a great decrease of theentire wafer temperature, the present applicant has developed atechnique in which a first focus ring (hereinafter, referred to as an“inner focus ring”) is provided and a second focus ring (hereinafter,referred to as an “outer focus ring”) is placed at an outside of thefirst focus ring, and the first focus ring is cooled whereas the outerfocus ring is not cooled but it is rather heated (see, for example,Patent Document 1).

Patent Document 1: US Patent Publication No. US 2010/0213171 A1

Generally, in a gap between two members having greatly differenttemperatures, deposits are likely to adhere to a member having a lowertemperature. Actually, the present inventor has found out that, when theaforementioned so-called dual focus ring including the inner focus ringand the outer focus ring is used, deposits tends to easily adhere to theinner focus ring in a gap between the inner and outer focus rings

Since the gap between the inner focus ring and the outer focus ring isnarrow and the plasma cannot be introduced into the gap easily, it isdifficult to remove the deposits adhering to the inner focus ring byasking or the like. Thus, in order to remove the deposits from the innerfocus ring, it is required that a chamber is opened to the atmosphereand the inner focus ring is taken out. As a result, an operation rate ofa substrate processing apparatus including the focus ring would bedeteriorated.

Further, in the substrate processing apparatus, a susceptor on which theinner focus ring or the outer focus ring are mounted is cooled to atemperature lower than the temperature of the inner focus ring.Accordingly, a temperature difference between the inner focus ring andthe susceptor is increased. As a result, deposits adhere to thesusceptor in a gap between the inner focus ring and the susceptor.

Since the gap between the focus ring and the susceptor is also narrow,in order to remove the deposits from the susceptor, it is required thechamber is opened to the atmosphere and the inner focus ring is takenout to expose the susceptor. As a result, the operation rate of thesubstrate processing apparatus would be also deteriorated.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing problems, the present disclosure provides afocus ring capable of preventing deposits from adhering to a memberhaving a lower temperature in a gap between two members having differenttemperatures. Further, the present disclosure also provides a substrateprocessing apparatus having this focus ring.

In accordance with one aspect of the present disclosure, there isprovided a focus ring disposed to surround a peripheral portion of asubstrate in a processing chamber of a substrate processing apparatus.The focus ring includes an inner focus ring placed adjacent to thesubstrate and configured to be cooled; an outer focus ring placed so asto surround the inner focus ring and configured not to be cooled; and aquartz member placed in a gap between the inner focus ring and the outerfocus ring.

Further, the quartz member may be exposed to a processing space in whichplasma is generated within the processing chamber.

Here, a mounting table for mounting thereon the substrate and the innerfocus ring may be provided within the processing chamber, and the quartzmember may be extended to be placed between the inner focus ring and themounting table.

In accordance with another aspect of the present disclosure, there isprovided a substrate processing apparatus that includes a processingchamber for accommodating a substrate therein; and a focus ring disposedto surround a peripheral portion of a substrate in the processingchamber. Here, the focus ring includes an inner focus ring placedadjacent to the substrate and configured to be cooled; an outer focusring placed so as to surround the inner focus ring and configured not tobe cooled; and a quartz member placed in a gap between the inner focusring and the outer focus ring.

In accordance with still another aspect of the present disclosure, thereis provided a substrate processing apparatus that includes a processingchamber for accommodating a substrate therein; a focus ring configuredto surround a peripheral portion of the substrate disposed in theprocessing chamber; and a mounting table for mounting thereon thesubstrate and the focus ring. Here, the focus ring includes an innerfocus ring placed adjacent to the substrate and configured to be cooled,and an outer focus ring placed so as to surround the inner focus ringand configured not to be cooled. Further, the mounting table isconfigured to be cooled such that a temperature of the mounting tablebecomes lower than that of the inner focus ring, and a quartz member isplaced in a gap between the inner focus ring and the mounting table.

In the substrate processing apparatus, the quartz member may be placedbetween the inner focus ring and a mounting surface of the mountingtable on which the inner focus ring is mounted.

Further, the quartz member may be extended to be placed in a gap betweenthe inner focus ring and the outer focus ring. Alternatively, a quartzmember may be further provided in a gap between the inner focus ring andthe outer focus ring.

In accordance with still another aspect of the present disclosure, thereis provided a processing chamber for accommodating a substrate therein;a focus ring disposed to surround a peripheral portion of the substratein the processing chamber; a mounting table for mounting thereon thesubstrate and the focus ring; and a gas supply unit configured to supplya gas into a gap between the focus ring and the mounting table. Here,the focus ring includes an inner focus ring placed adjacent to thesubstrate and configured to be cooled; and an outer focus ring placed soas to surround the inner focus ring and configured not to be cooled.Further, the gas supply unit is configured to supply the gas into atleast one of a gap between the inner focus ring and the outer focus ringand a gap between the inner focus ring and the mounting table.

The gas supplied by the gas supply unit may include an oxygen gas.

The gas supplied by the gas supply unit may be an inert gas.

The gas supplied by the gas supply unit may be a processing gas.

In accordance with still another aspect of the present disclosure, thereis provided a focus ring disposed to surround a peripheral portion of asubstrate in a processing chamber of a substrate processing apparatus.The focus ring includes an inner focus ring placed adjacent to thesubstrate and configured to be cooled; and an outer focus ring placed soas to surround the inner focus ring and configured not to be cooled.Here, the inner focus ring has a thin-plate shape flange exposed to aprocessing space within the processing chamber and protruded so as tocover a part of the outer focus ring.

The flange of the inner focus ring may have a thickness ranging fromabout 1.7 mm to about 2.0 mm.

In accordance with still another aspect of the present disclosure, thereis provided a substrate processing apparatus that includes a processingchamber for accommodating a substrate therein; and a focus ring disposedto surround a peripheral portion of the substrate in the processingchamber. Here, the focus ring includes an inner focus ring placedadjacent to the substrate and configured to be cooled; and an outerfocus ring placed so as to surround the inner focus ring and configurednot to be cooled; and the inner focus ring has a thin-plate shape flangeexposed to a processing space within the processing chamber andprotruded so as to cover a part of the outer focus ring.

In accordance with the present disclosure, since the quartz member isdisposed between the inner focus ring and the outer focus ring, theoxygen radicals are generated when the plasma comes into contact withthe quartz member in the gap between the inner focus ring and the outerfocus ring. The oxygen radicals may easily decompose and removedeposits, so that it can be prevented that the deposits adhere to theinner focus ring having a lower temperature in the gap between the innerfocus ring and the outer focus ring of which temperatures are greatlydifferent.

Further, in accordance with the present disclosure, since the quartzmember is disposed between the inner focus ring and the mounting table,the oxygen radicals are generated when the plasma comes into contactwith the quartz member in the gap between the inner focus ring and themounting table. The oxygen radicals may easily decompose and removedeposits, so that it can be prevented that the deposits adhere to themounting table having a lower temperature in the gap between the innerfocus ring and the mounting table of which temperatures are greatlydifferent.

Moreover, in accordance with the present disclosure, since the gassupply unit supplies the gas into at least one of the gap between theinner focus ring and the outer focus ring and the gap between the innerfocus ring and the mounting table, the supplied gas may push outreaction products, as a source of deposits, that have entered the gapbetween the inner focus ring and the outer focus ring or the gap betweenthe inner focus ring and the mounting table. Accordingly, it may bepossible to prevent deposits from adhering to the inner focus ringhaving the lower temperature in the gap between the inner focus ring andthe outer focus ring of which temperatures are greatly different.Likewise, it may also be possible to prevent deposits from adhering tothe mounting table having the lower temperature in the gap between theinner ring and the mounting table of which temperatures are greatlydifferent.

In addition, in accordance with the present disclosure, the inner focusring has the thin-plate shape flange exposed to the processing spacewithin the processing chamber and protruded so as to cover the outerfocus ring. Therefore, the temperature of the flange may be increased byreceiving radiant heat from the plasma in the processing space, so thata temperature difference between the inner focus ring and the outerfocus ring can be reduced in the vicinity of the flange. As a result, atleast in the vicinity of the flange, it may be possible to preventdeposits from adhering to the inner focus ring having the lowertemperature in the gap between the inner focus ring and the outer focusring.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments will be described inconjunction with the accompanying drawings. Understanding that thesedrawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be intended to limit its scope,the disclosure will be described with specificity and detail through useof the accompanying drawings, in which:

FIG. 1 is a schematic configuration view of a substrate processingapparatus in accordance with a first embodiment of the presentdisclosure;

FIG. 2 provides enlarged cross sectional views schematicallyillustrating configurations of a focus ring in the substrate processingapparatus of FIG. 1; FIG. 2(A) shows a focus ring in accordance with thefirst embodiment of the present disclosure; FIG. 2(B), a firstmodification example of the focus ring in accordance with the firstembodiment; FIG. 2(C), a second modification example of the focus ringin accordance with the first embodiment; FIG. 2(D), a third modificationexample of the focus ring in accordance with the first embodiment; FIG.2(E), a fourth modification example of the focus ring in accordance withthe first embodiment; and FIG. 2(F), a fifth modification example of thefocus ring in accordance with the first embodiment;

FIG. 3 provides an enlarged cross sectional views schematicallyillustrating configurations of a focus ring in a substrate processingapparatus in accordance with a second embodiment of the presentdisclosure; FIG. 3(A) shows a focus ring in accordance with the secondembodiment of the present disclosure; FIG. 3(B), a first modificationexample of the focus ring in accordance with the second embodiment; FIG.3(C), a second modification example of the focus ring in accordance withthe second embodiment; and FIG. 3(D), a third modification example ofthe focus ring in accordance with the second embodiment;

FIG. 4 provides enlarged cross sectional views schematicallyillustrating configurations of a focus ring in a substrate processingapparatus in accordance with a third embodiment of the presentdisclosure; FIG. 4(A) shows a focus ring in accordance with the thirdembodiment of the present disclosure and FIG. 4(B) shows a firstmodification example of the focus ring in accordance with the thirdembodiment;

FIG. 5 is an enlarged cross sectional view schematically illustrating aconfiguration of a focus ring in a substrate processing apparatus inaccordance with a fourth embodiment of the present disclosure;

FIG. 6 provides enlarged cross sectional views illustrating aconfiguration in the vicinity of a focus ring in a substrate processingapparatus capable of removing an attached deposit; FIG. 6(A) depicts afirst example and FIG. 6(B) depicts a second example;

FIG. 7 provides enlarged cross sectional views illustrating aconfiguration in the vicinity of a focus ring in a substrate processingapparatus capable of removing an attached deposit; FIG. 7(A) depicts athird example and FIG. 7(B) depicts a fourth example; and

FIG. 8 provides enlarged cross sectional views illustrating aconfiguration in the vicinity of a focus ring included in a substrateprocessing apparatus capable of removing an attached deposit; FIG. 8(A)depicts a fifth example; FIG. 8(B), a sixth example; FIG. 8(C), aseventh example; and FIG. 8(D), an eighth example.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, illustrative embodiments of the present disclosure will bedescribed with reference to the accompanying drawings.

First, a substrate processing apparatus in accordance with a firstembodiment of the present disclosure will be explained.

FIG. 1 is a schematic configuration view of the substrate processingapparatus in accordance with the first embodiment. The substrateprocessing apparatus is configured to perform a plasma etching processon a wafer as a substrate for a semiconductor device (hereinafter,simply referred to as a “wafer”).

Referring to FIG. 1, a substrate processing apparatus 10 includes achamber 11 for accommodating therein a wafer W having a diameter of,e.g., about 300 mm. A circular column-shaped susceptor 12 (mountingtable) for mounting thereon the wafer W is provided in the chamber 11.In this substrate processing apparatus 10, a side exhaust path 13 isformed between an inner sidewall of the chamber 11 and a side surface ofthe susceptor 12. An exhaust plate 14 is provided on the way of the sideexhaust path 13.

The exhaust plate 14 is a plate-shaped member having a multiple numberof through holes. The exhaust plate 14 serves as a partition plate thatpartitions an inside of the chamber 11 into an upper portion and a lowerportion. As will be described later, plasma is generated in an innerspace (processing space) within the upper portion 15 (hereinafter,referred to as a “processing chamber”) of the chamber 11 above theexhaust plate 14. Further, an exhaust pipe 17 for exhausting a gaswithin the chamber 11 is connected to the lower portion 16 (hereinafter,referred to as an “exhaust chamber (manifold)”) of the inside of thechamber 11 below the exhaust plate 14. The exhaust plate 14 confines orreflects the plasma generated in the processing chamber 15, thuspreventing leakage of the plasma into the manifold 16.

The exhaust pipe 17 is connected with a TMP (Turbo Molecular Pump) and aDP (Dry Pump) (both are not shown). These pumps evacuate anddepressurize the inside of the chamber 11. To elaborate, the DPdepressurizes the inside of the chamber 11 to an intermediate vacuumstate (e.g., about 1.3×10 Pa (0.1 Torr) or less) from an atmosphericpressure. Further, in cooperation with the DP, the TMP furtherdepressurizes the inside of the chamber 11 to a high vacuum state (e.g.,about 1.3×10⁻³ Pa (1.0×10⁻⁵ Torr) or less) lower than the intermediatepressure state. The internal pressure of the chamber 11 is controlled byan APC valve (not shown).

The susceptor 12 within the chamber 11 is connected with a first highfrequency power supply 18 via a first matching unit 19 and alsoconnected with a second high frequency power supply 20 via a secondmatching unit 21. The first high frequency power supply 18 is configuredto apply a high frequency power of a relatively low frequency for ionattraction (e.g., about 2 MHz) to the susceptor 12, and the second highfrequency power supply 20 is configured to apply a high frequency powerof a relatively high frequency for plasma generation (e.g., about 60MHz) to the susceptor 12. In this configuration, the susceptor 12 mayserve as an electrode. Further, the first and second matching units 19and 21 may reduce reflection of the high frequency powers from thesusceptor 12, thus improving the efficiency of applying the highfrequency powers to the susceptor 12.

A step-shaped portion is formed at a periphery of a top portion of thesusceptor 12 such that a central portion of the susceptor 12 protrudesupward. Provided at a top end of the central portion of the susceptor 12is an electrostatic chuck 23 made of ceramics and having anelectrostatic electrode plate 22 therein. The electrostatic electrodeplate 22 is connected with a DC power supply 24. If a positive DCvoltage is applied to the electrostatic electrode plate 22, a negativepotential would be generated in a surface (hereinafter, referred to as a“rear surface”) of the wafer W facing the electrostatic chuck 23.Therefore, a potential difference is generated between the electrostaticelectrode plate 22 and the rear surface of the wafer W. As a result, thewafer W can be attracted to and held on the electrostatic chuck 23 by aCoulomb force or a Johnsen-Rahbek force generated by the potentialdifference.

Further, the susceptor 12 has therein a cooling device (not shown) of acoolant path. In the present embodiment, the cooling device isconfigured to absorb, via the susceptor 12, heat of the wafer W of whichtemperature increases as a result of its contact with the plasma.Therefore, the temperature of the wafer W is prevented from increasingover a desired level.

The susceptor may be made of a conductor such as aluminum inconsideration of its heat transfer efficiency or its function as anelectrode. Further, in order to prevent the conductor from being exposedto the processing chamber 15 in which the plasma is generated, disposedat the side surface of the susceptor 12 is a side protection member 26made of a dielectric material such as, but not limited to, quartz(SiO₂).

A focus ring 25 is placed on the step-shaped portion (mounting surface)of the susceptor 12 and the side protection member 26 so as to surroundthe wafer W attracted to and held on the electrostatic chuck 23. Thefocus ring 25 may be a dual focus ring including an inner focus ring 25a surrounding the wafer W and an outer focus ring 25 b surrounding theinner focus ring 25 a. The inner focus ring 25 a and the outer focusring 25 b may be made of, but not limited to, silicon (Si) or siliconcarbide (SiC). That is, since the focus ring 25 is made of asemiconductor, a distribution range of the plasma can be expanded toabove the focus ring 25 as well as above the wafer W. Thus, a plasmadensity in a region above a periphery portion of the wafer W can bemaintained at the substantially same level as a plasma density in aregion above a central portion of the wafer W. Accordingly, it ispossible to uniformly perform the plasma etching process on the entiresurface of the wafer W.

The inner focus ring 25 a is mainly mounted on the step-shaped portionof the susceptor 12. Meanwhile the outer focus ring 25 b is mainlymounted on the side protection member 26. Further, a heat transfer sheet34 made of, e.g., silicon rubber having heat transfer property isprovided between the inner focus ring 25 a and the susceptor 12, asshown in FIG. 2(A) to be described later. Heat of the inner focus ring25 a, of which temperature increases as a result of the contact with theplasma, is transferred to the susceptor 12 via the heat transfer sheet34 and then absorbed by the cooling device of the susceptor 12.Meanwhile, since no element is provided between the outer focus ring 25b and the side protection member 26, if the inner space of theprocessing chamber 15 is depressurized, a heat insulating vacuum layeris formed between the outer focus ring 25 b and the side protectionmember 26. Accordingly, heat of the outer focus ring 25 b, of whichtemperature increases as a result of the contact with the plasma, is nottransferred to the side protection member 26. As a result, the outerfocus ring 25 b is not cooled, and, thus, the temperature of the outerfocus ring 25 b is maintained at a high level. Accordingly, thetemperature of the inner focus ring 25 a can be maintained at a desiredlow level, while the temperature of the outer focus ring 25 b can bemaintained at the high level.

A shower head 27 is provided at a ceiling of the chamber 11 so as toface the susceptor 12. The shower head 27 includes an upper electrodeplate 28, a cooling plate 29 that supports the upper electrode plate 28in a detachable manner, and a cover 30 that covers the cooling plate 29.The upper electrode plate 28 is a circular plate-shaped member having amultiple number of gas holes 31 formed in a thickness direction thereof.A buffer room 32 is provided within the cooling plate 29, and aprocessing gas inlet pipe 33 is connected to the buffer room 32.

In the substrate processing apparatus, a processing gas supplied intothe buffer room 32 via the processing gas inlet pipe 33 is introducedinto the inner space of the processing chamber 15 through the gas holes31. The introduced processing gas is excited into plasma by the highfrequency power for plasma generation applied into the inner space ofthe processing chamber 15 from the second high frequency power supply 20via the susceptor 12. Ions in the plasma are attracted toward the waferW by the high frequency power for ion attraction applied to thesusceptor 12 from the first high frequency power supply 18, and, thus,the plasma etching process is performed on the wafer W.

While the plasma etching process is being performed on the wafer W,reaction products generated as a result of a reaction between an etchingtarget layer of the wafer W and the plasma float in the inner space ofthe processing chamber 15 and adhere to parts of the processing chamber15 as deposits. Especially, the deposits tend to adhere to a memberhaving a lower temperature in a gap between two members of whichtemperatures are greatly different. Accordingly, in a gap between theinner focus ring 25 a and the outer focus ring 25 b, the deposits mayadhere to the inner focus ring 25 a. Since the gap between the innerfocus ring 25 a and the outer focus ring 25 b is narrow and has alabyrinth structure, it may be difficult to remove the deposits adheringto the inner focus ring 25 a.

In order to solve this problem, in accordance with the first embodiment,a member made of quartz is disposed in the gap between the inner focusring 25 a and the outer focus ring 25 b.

FIG. 2 provides enlarged cross sectional views illustrating schematicconfigurations of a focus ring in the substrate processing apparatus ofFIG. 1. FIG. 2(A) shows a focus ring in accordance with the firstembodiment of the present disclosure; FIG. 2(B), a first modificationexample of the focus ring in accordance with the first embodiment; FIG.2(C), a second modification example of the focus ring in accordance withthe first embodiment; FIG. 2(D), a third modification example of thefocus ring in accordance with the first embodiment; FIG. 2(E), a fourthmodification example of the focus ring in accordance with the firstembodiment; and FIG. 2(F), a fifth modification example of the focusring in accordance with the first embodiment.

Referring to FIG. 2(A), a focus ring 25 has a block member 25 c (quartzmember) made of quartz and disposed in a gap between the inner focusring 25 a and the outer focus ring 25 b (hereinafter, referred to as a“first gap”).

When a plasma etching process is performed in the substrate processingapparatus 10, if plasma, especially, radicals enter the first gap tocome into contact with the block member 25 c, the radicals chemicallyreact with the quartz to generate oxygen radicals from the block member25 c. If reaction products adhere to the inner focus ring 25 a asdeposits in the first gap, the oxygen radicals immediately make achemical reaction with the deposits, so that the deposits are decomposedto be removed. Accordingly, it is possible to prevent the deposits fromadhering to the inner focus ring 25 a in the first gap.

It is possible to prevent the deposits from adhering to the inner focusring 25 a only if the oxygen radicals are generated in the first gap.Thus, there will be no specific limit in the shape or the size of theblock member 25 c as long as the block member 25 c is provided in thefirst gap. Accordingly, the block member 25 c may have various crosssectional shapes, such as a downwardly protruding cross sectional shape(FIG. 2(B)), an upwardly protruding cross sectional shape (FIG. 2(C)), arectangular cross sectional shape (FIG. 2(D)), and so forth. In anycase, however, it may be desirable that a part of the block member 25 cis exposed to the inner space of the processing chamber 15. In this way,the block member 25 c can be effectively contacted with the plasma, and,thus, the oxygen radicals can be sufficiently generated from the blockmember 25 c. Alternatively, if the block member 25 c can make a contactwith the plasma that enters the first gap, the block member 25 c may notbe directly exposed to the inner space of the processing chamber 15(FIG. 2(E)).

Moreover, the block member 25 c may be extended to be also placedbetween a bottom surface of the inner focus ring 25 a and thestep-shaped portion of the susceptor 12 (FIG. 2(F)). By providing theblock member 25 c in this way, it is possible to prevent reactionproducts as a source of deposits from entering a gap between the bottomsurface of the inner focus ring 25 a and the step-shaped portion of thesusceptor 12. Moreover, since the block member 25 c also generatesoxygen radicals between the bottom surface of the inner focus ring 25 aand the step-shaped portion of the susceptor 12, decomposition andremoval of the deposits by the oxygen radicals can be facilitated in thegap between the bottom surface of the inner focus ring 25 a and thestep-shaped portion of the susceptor 12. In addition, in thisconfiguration, heat transfer sheets 34 a and 34 b may be disposedbetween the step-shaped portion of the susceptor 12 and the block member25 c and between the block member 25 c and the inner focus ring 25 a,respectively.

Since the block member 25 c is made of quartz, silicon radicals as wellas the oxygen radicals may be generated when the block member 25 c makesa chemical reaction with the plasma. Since the silicon radicals maycombine with a silicon simple substance or an oxygen gas to adhere tomembers within the processing chamber 15 as silicon oxide, it may bedesirable to introduce a carbon fluoride (CF)-based processing gas intothe inner space of the processing chamber 15. As a result, since plasmagenerated from the carbon fluoride-based processing gas decomposessilicon or silicon carbide, it is possible to prevent the silicon orsilicon carbide from adhering to the members.

Now, a substrate processing apparatus in accordance with a secondembodiment of the present disclosure will be described.

Since a configuration and an operation of the second embodiment arebasically the same as those of the above-described first embodiment,redundant description will be omitted and only distinctive configurationand operation will be elaborated.

In the substrate processing apparatus 10 of FIG. 1, a gap having acertain width is formed between the side surface of the susceptor 12 andan inner side surface of an inner focus ring 25 a in order to easilyattach and detach a focus ring 25 to/from the susceptor 12. Since thesusceptor 12 is directly cooled by the cooling device embedded therein,a temperature of the susceptor 12 becomes considerably lower than atemperature of the inner focus ring 25 a. That is, there may be a greattemperature difference between both sides of a gap between the sidesurface of the susceptor 12 and the inner side surface of the innerfocus ring 25 a (hereinafter, referred to as a “second gap”). As aresult, in the second gap, deposits may adhere to the susceptor 12.

In order to solve this problem, in accordance with the secondembodiment, a member made of quartz is disposed in the second gap.

FIG. 3 provides enlarged cross sectional views schematicallyillustrating configurations of a focus ring included in the substrateprocessing apparatus in accordance with the second embodiment. FIG. 3(A)shows a focus ring in accordance with the second embodiment of thepresent disclosure; FIG. 3(B), a first modification example of the focusring in accordance with the second embodiment; FIG. 3(C), a secondmodification example of the focus ring in accordance with the secondembodiment; and FIG. 3(D), a third modification example of the focusring in accordance with the second embodiment.

Referring to FIG. 3(A), the focus ring 25 includes a block member 25 d(quartz member) made of quartz and disposed in the second gap.

When a plasma etching process is performed in the substrate processingapparatus 10, if plasma, especially, radicals enter the second gap tocome into contact with the block member 25 d, oxygen radicals aregenerated from the block member 25 d. The oxygen radicals make achemical reaction with deposits in the second gap, so that the depositsare decomposed and removed. Accordingly, it is possible to prevent thedeposits from adhering to the susceptor 12 in the second gap. Here,there exists a great temperature difference between both sides of thesecond gap.

It is possible to prevent the deposits from adhering to the susceptor 12only if the oxygen radicals are generated in the second gap. Thus, therewill be no specific limit in the shape or the size of the block member25 d as long as the block member 25 d is provided in the second gap.Moreover, the block member 25 d may also be provided between the bottomsurface of the inner focus ring 25 a and the step-shaped portion of thesusceptor 12 (FIG. 3(B)). By providing the block member 25 d in thisway, it is possible to prevent reaction products as a source of depositsfrom entering the gap between the bottom surface of the inner focus ring25 a and the step-shaped portion of the susceptor 12. Moreover, sincethe block member 25 d also generates oxygen radicals between the bottomsurface of the inner focus ring 25 a and the step-shaped portion of thesusceptor 12, decomposition and removal of the deposits by the oxygenradicals can be facilitated in the gap between the bottom surface of theinner focus ring 25 a and the step-shaped portion of the susceptor 12.In this case, the heat transfer sheets 34 a and 34 b may be disposedbetween the step-shaped portion of the susceptor 12 and a bottom surfaceof the block member 25 d and between a top surface of the block member25 d and the inner focus ring 25 a, respectively.

Moreover, the block member 25 d may be extended to be placed in thefirst gap (FIG. 3(B)). With this configuration, it may be possible toprevent deposits from adhering to members in both the first gap and thesecond gap.

In addition, the focus ring 25 may have a block member 25 c as describedin the first embodiment as well as the block member 25 d (FIG. 3(C)).Further, the block member 25 d may also be provided between a bottomsurface of the outer focus ring 25 b and a side protection member 26 aswell as between the bottom surface of the inner focus ring 25 a and thestep-shaped portion of the susceptor 12 (FIG. 3(D)).

Subsequently, a substrate processing apparatus in accordance with athird embodiment will be described.

Since a configuration and an operation of the third embodiment arebasically the same as those of the above-described first embodiment,redundant description thereof will be omitted and only distinctiveconfiguration and operation will be elaborated.

FIG. 4 provides enlarged cross sectional views schematicallyillustrating configurations of a focus ring in the substrate processingapparatus in accordance with the third embodiment. FIG. 4(A) illustratesa focus ring in accordance with third second embodiment, and FIG. 4(B)illustrates a first modification example of the focus ring in accordancewith the third embodiment.

Referring to FIG. 4(A), the substrate processing apparatus 10 includes agas supply port 35 (gas supply device) that is opened at the step-shapedportion of the susceptor 12 and faces the bottom surface of the innerfocus ring 25 a. The gas supply port 35 supplies a certain gas, e.g., anoxygen gas toward the bottom surface of the inner focus ring 25 a when aplasma etching process or a cleaning process using plasma such as WLDC(Wafer Less Dry Cleaning) process is performed in the substrateprocessing apparatus 10. The supplied oxygen gas (indicated by arrows inFIG. 4) flows between the step-shaped portion of the susceptor 12 andthe bottom surface of the inner focus ring 25 a and is supplied into atleast one of the first and second gaps.

The oxygen gas supplied into the first or the second gap comes intocontact with plasma that has entered the first or the second gap, sothat oxygen radicals are generated. These oxygen radicals make achemical reaction with deposits in the first or the second gap, and,thus, the deposits are decomposed to be removed. As a result, in thefirst or second gap where there exists a great temperature difference,it is possible to prevent the deposits from adhering to the susceptor 12or the inner focus ring 25 a. Moreover, the oxygen gas supplied into thefirst or the second gap pushes out reaction products, which have enteredthe first or the second gap and would become a source of the deposits,into the inner space of the processing chamber 15. Accordingly, it ispossible to further effectively prevent adhesion of the deposits in thefirst or the second gap.

In the above-described third embodiment, although the gas supply port 35is formed in the step-shaped portion of the susceptor 12, the positionof the gas supply port 35 may not be limited to the step-shaped portionof the susceptor 12 as long as the gas from the gas supply port 35 canbe supplied into the first or the second gap. By way of non-limitingexample, the gas supply port 35 may be formed between the susceptor 12and the side protection member 26 (FIG. 4(B)), or may be formed in theside protection member 26 (not shown).

Further, the gas supplied from the gas supply port 35 may not be limitedto the oxygen gas. By way of non-limiting example, an inert gas such asa rare gas, a nitrogen gas, or a processing gas may be supplied instead.The inert gas serves to push out the reaction products that have enteredthe first or the second gap. Further, since the inert gas does not reactwith the plasma introduced into the first or second gap, any newreaction products are not produced. Accordingly, it is possible to moreeffectively prevent adhesion of the deposits in the first or the secondgap. Likewise, the processing gas also serves to push out the reactionproducts entering the first or the second gap. Further, even if theprocessing gas is introduced into the inner space of the processingchamber 15, it may not affect components of the plasma. Thus, unintendedplasma etching may not be performed on the wafer W.

In addition, if the oxygen gas or the processing gas is introduced intothe inner space of the processing chamber 15 when these gases aresupplied from the gas supply port 35, plasma density or plasmadistribution in the inner space of the processing chamber 15 may beaffected. In order to solve this problem, in the substrate processingapparatus 10, it may be desirable to reduce an amount of the oxygen gasor the processing gas supplied from a part of a shower head 27corresponding to the first or the second gap.

Now, a substrate processing apparatus in accordance with a fourthembodiment of the present disclosure will be explained.

Since a configuration and an operation of the fourth embodiment arebasically the same as those of the above-described first embodiment,redundant description thereof will be omitted and only distinctiveconfiguration and operation will be elaborated.

FIG. 5 is an enlarged cross sectional view schematically illustrating aconfiguration of a focus ring in the substrate processing apparatus inaccordance with the fourth embodiment.

Referring to FIG. 5, an inner focus ring 25 a has a thin plate-shapedflange 25 e (protrusion) on the side of the inner space of theprocessing chamber 15. The flange 25 e is exposed to the inner space ofthe processing chamber 15 and protrudes so as to cover all or a part ofthe outer focus ring 25 b. A first gap is formed between the flange 25 eand a surface of the outer focus ring 25 b facing the flange 25 e. Athickness of the flange 25 e may be set to be in the range of, but notlimited to, about 1.7 mm to about 2.0 mm.

Since the flange 25 e is thin, heat capacity thereof is small and atemperature thereof is increased higher than that of the remaining partof the inner focus ring 25 a by radiant heat from plasma when a plasmaetching process or a WLDC process is performed in the substrateprocessing apparatus 10. As a result, in the first gap, a temperaturedifference between the inner focus ring 25 a and the outer focus ring 25b can be reduced, so that it becomes possible to prevent deposits fromadhering to the inner focus ring 25 a in the first gap. Moreover, evenif deposits are attached to the inner focus ring 25 a in the first gap,the deposits may be decomposed and removed by radiant heat from theflange 25 e or the outer focus ring 25 b having high temperatures.

In accordance with the fourth embodiment, since the flange 25 e isformed to cover all or a part of the outer focus ring 25 b, the firstgap may have a labyrinth structure. As a result, it may be difficult forreaction products as a source of deposits to enter the first gap towardthe side of the susceptor 12, and, thus, adhesion of deposits in thefirst gap can be prevented.

Moreover, since a minimum thickness of the flange 25 e is e.g., about1.7 mm, it can be possible to prevent the strength of the flange 25 efrom being critically decreased, and to prevent the flange 25 e frombeing broken or damaged while the inner focus ring 25 a is beingreplaced. Furthermore, since a maximum thickness of the flange 25 e is,e.g., about 2.0 mm, it can be prevented that the heat capacity of theflange 25 e increases beyond a certain level. As a result, it ispossible to effectively increase the temperature of the flange 25 e bythe radiant heat from the plasma.

Although there has been described the present disclosure for therespective embodiments, the present disclosure may not be limited to theaforementioned embodiments.

Further, the above-described embodiments may be applicable not only tothe plasma processing apparatus 10 configured to perform a plasmaetching process on a wafer W for a semiconductor device but also to aplasma processing apparatus configured to process various types ofsubstrates for use in a FPD (Flat Panel Display) including a LCD (LiquidCrystal Display), a photo mask, a CD substrate, a printed substrate, andthe like by using plasma.

In the above, there have been described embodiments capable ofpreventing adhesion of deposits in the first or the second gap. Forexample, however, if a large quantity of reaction products is generatedin the plasma etching process, it may be not possible to completelyprevent the adhesion of the deposits in the first or second gap even inaccordance with the above-described embodiments.

Below, an example substrate processing apparatus capable of removingdeposits in the first or second gap will be elaborated. Examples to bedescribed below can be used together with any of the above-describedembodiments of the present disclosure.

FIG. 6 presents enlarged cross sectional views each schematicallyillustrating a configuration in the vicinity of a focus ring in asubstrate processing apparatus capable of removing attached deposits.FIG. 6(A) shows a first example and FIG. 6(B) shows a second example.

Referring to FIG. 6(A), the side protection member 26 has a protrusion26 a. The protrusion 26 a is made of material capable of transmitting alaser beam, e.g., quartz and is formed to upwardly protrude toward afirst gap. The protrusion 26 a has a facing surface 26 b facing an innerfocus ring 25 a in a first gap. Further, a first laser beam irradiationdevice (not shown) is provided below the side protection member 26, andthe first laser beam irradiation device is configured to irradiate alaser beam 36 for heating the focus ring toward the side protectionmember 26. By way of non-limiting example, the laser beam 36 may have awavelength equal to or smaller than about 1100 nm.

The laser beam 36 irradiated to the side protection member 26 isreflected at respective inner surfaces of the side protection member 26repetitively, and then, finally irradiated to the outer focus ring 25 bfrom an upper portion of the side protection member 26. Since the outerfocus ring 25 b is made of silicon or silicon carbide, the outer focusring 25 b can absorb the laser beam 36 having the wavelength equal to orsmaller than about 1100 nm. As a result, the outer focus ring 25 b maybe heated by the absorbed laser beam 36. At this time, since the facingsurface 26 b of the protrusion 26 a faces the inner focus ring 25 a inthe first gap, a part of the laser beam 36 is irradiated toward theinner focus ring 25 a from the facing surface 26 b. The part of thelaser beam irradiated to the inner focus ring 25 a can be absorbed bythe deposits adhering to the inner focus ring 25 a, so that atemperature of the deposits is increased. As a result, it is possible toeasily decompose and remove the deposits, so that the deposits adheringto the inner focus ring 25 a having a lower temperature in the first gapcan be removed.

Further, if the temperature of the deposits is not sufficientlyincreased because a light amount of a part of the laser beam 36 forheating the focus ring irradiated to the inner focus ring 25 a is small,a laser beam different from the laser beam 36 for heating the focusring, e.g., a laser beam capable of being efficiently absorbed by thedeposits may also be irradiated to the side protection member 26, and apart of this another laser beam may be irradiated toward the inner focusring 25 a from the facing surface 26 b. In this way, the temperature ofthe deposits can be increased sufficiently and efficiently.

Moreover, in case that a laser beam cannot be directly irradiated to thefirst gap, for example, in case that the first gap has a labyrinthstructure, a laser beam guide member 37 (laser beam transmitting member)may be provided between a susceptor 12 and the side protection member 26so as to face the first gap, as illustrated in FIG. 6(B). The laser beamguide member 37 is made of quartz and provided as a separate member fromthe side protection member 26. Further, a second laser beam irradiationdevice (not shown) may be provided under the laser beam guide member 37.This second laser beam irradiation device may be configured to irradiatea laser beam 38 having a wavelength larger than, e.g., about 1100 nmtoward the laser beam guide member 37.

The laser beam 38 irradiated to the laser beam guide member 37 isrepetitively reflected at respective inner surfaces of the laser beamguide member 37 while it passes through the laser beam guide member 37,and then, finally irradiated to the first gap from an upper portion ofthe laser beam guide member 37. Here, since the first gap has alabyrinth structure, a part of the inner focus ring 25 a or a part ofthe outer focus ring 25 b may be located on a travel path of the laserbeam 38. Since a laser beam having a wavelength larger than about 1100nm may pass through the silicon or silicon carbide, the laser beam 38may reach the first gap through the part of the inner focus ring 25 a orthe part of the outer focus ring 25 b. Then, the laser beam 38 may beabsorbed by the deposits in the first gap, so that a temperature of thedeposit is increased. As a result, the deposits in the first gap can beremoved.

Moreover, in case that a component or a member for absorbing the laserbeam is not provided between the first gap and the second laser beamirradiation device, the second laser beam irradiation device may beprovided at a vicinity of a sidewall of the chamber 11 or at a vicinityof a cover at the top of the chamber 11 as well as provided below thelaser beam guide member 37. In this case, it may be desirable to disposethe second laser beam irradiation device to face the first gap.

FIG. 7 provides enlarged cross sectional views each schematicallyillustrating a configuration in the vicinity of a focus ring in asubstrate processing apparatus capable of removing attached deposits.FIG. 7(A) shows a third example, and FIG. 7(B) shows a fourth example.

As depicted in FIG. 7(A), the substrate processing apparatus 10 furtherincludes a pusher pin 39 configured to be protruded from the step-shapedportion of the susceptor 12. When the pusher pin 39 protrudes upwardly,the pusher pin 39 lifts up the inner focus ring 25 a away from the outerfocus ring 25 b. Typically, if deposits come into contact with plasma,the deposits make a chemical reaction with the plasma, especially,radicals therein, so that the deposits are decomposed to be removed.Here, since the inner focus ring 25 a lifted up by the pusher pin 39 isexposed to the plasma within the inner space of the processing chamber15, deposits adhering to the inner focus ring 25 a is easily decomposedand removed. As a result, it may be possible to remove deposits adheringto the inner focus ring 25 a having a lower temperature in the first gap

Moreover, referring to FIG. 7(B), the substrate processing apparatus 10further includes a pusher pin 40 configured to be protruded from the topsurface of the side protection member 26. When the pusher pin 40protrudes upwardly, the pusher pin 40 lifts up the outer focus ring 25 baway from the inner focus ring 25 b. In this example, since the outerfocus ring 25 b is spaced apart from the inner focus ring 25 a, depositsadhering to the inner focus ring 25 a are exposed to plasma within theinner space of the processing chamber 15. Accordingly, the depositsadhering to the inner focus ring 25 a of the lower temperature can beeasily decomposed and removed. As a result, it may be possible to removethe deposits adhering to the inner focus ring 25 a in the first gap.

The removal of the deposits in the third or fourth example may beperformed when a WLDC process is performed in the substrate processingapparatus 10. Further, in the third or fourth example, since the pusherpins are used as members for moving the inner focus ring 25 a or theouter focus ring 25 b, complication of the structure of the substrateprocessing apparatus 10 can be avoided.

FIG. 8 provides enlarged cross sectional views each schematicallyillustrating a configuration in the vicinity of a focus ring in asubstrate processing apparatus capable of removing attached deposits.FIG. 8(A) depicts a fifth example; FIG. 8(B), a sixth example; FIG.8(C), a seventh example; and FIG. 8(D), an eighth example.

Referring to FIG. 8(A), the substrate processing apparatus 10 furtherincludes a grounding member 41 made of a semiconductor or a conductor(e.g., silicon). The grounding member 41 is provided under the outerfocus ring 25 b at an outside of the side protection member 26. Anelectric potential of the grounding member 41 is maintained as a groundpotential.

In the present example, since the grounding member 41 is provided nearthe outer focus ring 25 b, an electric potential of the outer focus ring25 b may also become close to the ground potential. Meanwhile, since anegative bias potential is generated in the susceptor 12 or the innerfocus ring 25 a, the electric potential of the outer focus ring 25 bbecomes relatively higher, so that electrons can be easily attracted tothe outer focus ring 25 b. As a result, the thickness of a sheathcorresponding to the outer focus ring 25 b may be increased, and plasmain the inner space of the processing chamber 15 can be concentrated on aposition corresponding to the inner focus ring 25 a as compared to aposition corresponding to the outer focus ring 25 b. Accordingly, aplasma density corresponding to the first gap or the second gap can beincreased, so that plasma reaching the first or second gap can also beincreased. Consequently, deposits in the first or second gap by theplasma can be easily decomposed, so that it becomes possible to removedeposits adhering to the inner focus ring 25 a having a lowertemperature in the first gap and, also, deposits adhering to thesusceptor 12 having an even lower temperature in the second gap.

Referring to FIG. 8(B), the substrate processing apparatus 10 furtherincludes a ground electrode 42 having a ground potential. The groundelectrode 42 is provided within the side protection member 26 to belocated near a focus ring 25.

In this example, since the ground electrode 42 is provided near theouter focus ring 25 b, an electric potential of the outer focus ring 25b may also become close to the ground potential. As a result, the plasmain the inner space of the processing chamber 15 can be concentrated on aposition corresponding to the inner focus ring 25 a as compared to aposition corresponding to the outer focus ring 25 b. Accordingly, aplasma density corresponding to the first gap or the second gap can beincreased, so that it becomes possible to remove deposits adhering tothe inner focus ring 25 a having the lower temperature in the first gapand, also, deposits adhering to the susceptor 12 having the even lowertemperature in the second gap.

Referring to FIG. 8(C), the substrate processing apparatus 10 furtherincludes a positive potential electrode provided within the sideprotection member 26 to be located near the outer focus ring 25 b. Apositive voltage is applied to the positive potential electrode 43.

In the present example, since the positive potential electrode 43 isdisposed near the outer focus ring 25 b, the outer focus ring 25 b mayalso have a positive potential. As a result, the plasma in the innerspace of the processing chamber 15 can be further concentrated on aposition corresponding to the inner focus ring 25 a as compared to aposition corresponding to the outer focus ring 25 b. Accordingly, aplasma density corresponding to the first gap or the second gap can beincreased, so that it becomes possible to remove deposits adhering tothe inner focus ring 25 a having the lower temperature in the first gapand, also, deposits adhering to the susceptor 12 having the even lowertemperature in the second gap.

Referring to FIG. 8(D), the substrate processing apparatus 10 furtherincludes an electromagnet 44 provided in the vicinity of the first gapto be located below the focus ring 25.

In the present example, the electromagnet 44 may serve to generate amagnetic field around the first gap, thus concentrating the plasma inthe inner space of the processing chamber 15 on a position correspondingto the inner focus ring 25 a as compared to a position corresponding tothe outer focus ring 25 b. Accordingly, a plasma density correspondingto the first gap or the second gap can be increased, so that it becomespossible to remove deposits adhering to the inner focus ring 25 a havingthe lower temperature in the first gap and, also, deposits adhering tothe susceptor 12 having the even lower temperature in the second gap.

1. A focus ring disposed to surround a peripheral portion of a substratein a processing chamber of a substrate processing apparatus, the focusring comprising: an inner focus ring placed adjacent to the substrateand configured to be cooled; an outer focus ring placed so as tosurround the inner focus ring and configured not to be cooled; and aquartz member placed in a gap between the inner focus ring and the outerfocus ring.
 2. The focus ring of claim 1, wherein the quartz member isexposed to a processing space in which plasma is generated within theprocessing chamber.
 3. The focus ring of claim 1, wherein a mountingtable for mounting thereon the substrate and the inner focus ring isprovided within the processing chamber, and the quartz member isextended to be placed between the inner focus ring and the mountingtable.
 4. A substrate processing apparatus comprising: a processingchamber for accommodating a substrate therein; and a focus ring disposedto surround a peripheral portion of a substrate in the processingchamber, wherein the focus ring comprises: an inner focus ring placedadjacent to the substrate and configured to be cooled; an outer focusring placed so as to surround the inner focus ring and configured not tobe cooled; and a quartz member placed in a gap between the inner focusring and the outer focus ring.
 5. A substrate processing apparatuscomprising: a processing chamber for accommodating a substrate therein;a focus ring configured to surround a peripheral portion of thesubstrate disposed in the processing chamber; and a mounting table formounting thereon the substrate and the focus ring, wherein the focusring comprises: an inner focus ring placed adjacent to the substrate andconfigured to be cooled; and an outer focus ring placed so as tosurround the inner focus ring and configured not to be cooled, themounting table is configured to be cooled such that a temperature of themounting table becomes lower than that of the inner focus ring, and aquartz member is placed in a gap between the inner focus ring and themounting table.
 6. The substrate processing apparatus of claim 5,wherein the quartz member is placed between the inner focus ring and amounting surface of the mounting table on which the inner focus ring ismounted.
 7. The substrate processing apparatus of claim 6, wherein thequartz member is extended to be placed in a gap between the inner focusring and the outer focus ring.
 8. The substrate processing apparatus ofclaim 6, wherein a quartz member is further provided in a gap betweenthe inner focus ring and the outer focus ring.
 9. A substrate processingapparatus comprising: a processing chamber for accommodating a substratetherein; a focus ring disposed to surround a peripheral portion of thesubstrate in the processing chamber; a mounting table for mountingthereon the substrate and the focus ring; and a gas supply unitconfigured to supply a gas into a gap between the focus ring and themounting table, wherein the focus ring comprises an inner focus ringplaced adjacent to the substrate and configured to be cooled; and anouter focus ring placed so as to surround the inner focus ring andconfigured not to be cooled, and the gas supply unit is configured tosupply the gas into at least one of a gap between the inner focus ringand the outer focus ring and a gap between the inner focus ring and themounting table.
 10. The substrate processing apparatus of claim 9,wherein the gas supplied by the gas supply unit includes an oxygen gas.11. The substrate processing apparatus of claim 9, wherein the gassupplied by the gas supply unit is an inert gas.
 12. The substrateprocessing apparatus of claim 9, wherein the gas supplied by the gassupply unit is a processing gas.
 13. A focus ring disposed to surround aperipheral portion of a substrate in a processing chamber of a substrateprocessing apparatus, the focus ring comprising: an inner focus ringplaced adjacent to the substrate and configured to be cooled; and anouter focus ring placed so as to surround the inner focus ring andconfigured not to be cooled, wherein the inner focus ring has athin-plate shape flange exposed to a processing space within theprocessing chamber and protruded so as to cover a part of the outerfocus ring.
 14. The focus ring of claim 13, wherein the flange of theinner focus ring has a thickness ranging from about 1.7 mm to about 2.0mm.
 15. A substrate processing apparatus comprising: a processingchamber for accommodating a substrate therein; and a focus ring disposedto surround a peripheral portion of the substrate in the processingchamber, wherein the focus ring comprises: an inner focus ring placedadjacent to the substrate and configured to be cooled; and an outerfocus ring placed so as to surround the inner focus ring and configurednot to be cooled, and the inner focus ring has a thin-plate shape flangeexposed to a processing space within the processing chamber andprotruded so as to cover a part of the outer focus ring.